Sunscreen compositions depend for their efficacy on ultraviolet light absorbing chemical agents to block the erythemal (skin reddening) wave lengths of ultraviolet radiation. Zinc oxide, titanium dioxide and talc are representative of physical sun blocking agents and p-aminobenzoic acid (PABA) and its derivatives are representative of chemical sunscreen agents. An ideal sunscreen agent has a high extinction coefficient (absorptivity), and is non-photosensitizing, chemically stable, non-toxic and non-irritating. In addition, if it is desired to minimize washing off of the sunscreen composition while swimming or as the result of perspiration, sunscreen agents which are substantive to the skin are preferred over less water-resistant sunscreen compositions. Because sunscreens presently approved by the FDA are not by themselves substantive, carrier vehicles must be selected which increase substantivity. In many cases these are emulsions. If the vehicles are oil-based, the resulting composition necessarily will be oily and often tacky, characteristics which are usually undesirable. If, on the other hand, the vehicle is an oil in water emulsion, the result will be more elegant. Accordingly, careful attention in formulating is required in order to incorporate all ingredients uniformly into the composition and to form a stable emulsion.
The mode of application of the sunscreen composition imposes additional requirements on the sunscreen formulation. While application by hand, swab or spray is generally in use, it is now proposed, in accordance with the present invention, to apply a substantive sunscreen composition from a fibrous sheet uniformly impregnated with the composition and prepackaged in a vapor-and-water impermeable container such as a polyethylene envelope. Fibrous sheet applicator systems require, however, that a composition have a low viscosity for rapid and uniform diffusion throughout the applicator prior to packaging. Low viscosity in turn suggests that the composition have a high water and/or alcohol content. However, it is difficult to form stable emulsions of low viscosity sunscreen dispersions. Moreover, too much alcohol may destabilize emulsions and cause a burning sensation and undesirable drying of the skin. Too little alcohol reduces solvency and/or emulsifiability of some active ingredients in sunscreen compositions and dispersibility of the formulation in the fibrous sheet applicator. Nevertheless, a cosmetically acceptable alcohol is desirable in a sunscreen composition to aid in lowering the viscosity, to decrease the drying time, and to improve the feel of the composition (including the cooling effect resulting from evaporation).
A variety of sunscreen compositions have been developed as well as devices and materials for applying the products. For example, U.S. Pat. No. 4,559,225 to Fourman discloses a non-aqueous sunscreen composition containing 10-90 wt. % alcohol and a film-forming cellulosic polymer to render the composition resistant to removal by water.
U.S. Pat. No. 4,254,102 to Kaplan et al. describes the enhancement of substantivity of a sunscreen composition to wet skin by the incorporation of 2-6 wt. % of a solid fatty alcohol such as cetyl alcohol. The composition contains 45-65 wt. % water.
U.S. Pat. No. 4,069,309 to Ciaudelli et al. describes certain cationic para-amino benzoate esters which improve the resistance of sunscreen compositions to removal by moisture. Formulations are described containing water/alcohol proportions of 30/70 and 50/50 by weight.
U.S. Pat. No. 4,683,134 to Palinczar describes sunscreen compositions based upon a neutralized, cross-linked acrylic polymer, up to 90% by weight alcohol, an ethyoxylate fatty amine as a neutralizing agent for the polymer, and 2-10% by weight of water.
U.S. Pat. No. 3,185,628 to Fetscher et al describes sunscreens containing sulfone derivatives as the sunscreen agent. The compositions are emulsions. Example IX discloses a composition containing 50 wt. % alcohol and 45 wt. % water and Example X shows a composition containing no alcohol and 62 wt. % water.
U.S. Pat. No. 3,821,363 to Black et al. describes sunscreen gels based upon ethylene maleic acid anhydride copolymers. The formulations may contain 45-55 wt. % alcohol and 46-80 wt. % water (clear) or the same amount of water with no alcohol (opaque).
U.S. Pat. No. 3,103,682 to Markle discloses the application of suntanning oils or creams with an absorbent pad such as a plastic sponge.
The article "Sunscreen and Suntan Products" Handbook of Non-Prescription Drugs, American Pharmaceutical Association, by E. M. De Simone II, Chap. 26, pages 499-511, describes a variety of sunscreen formulations and selection criteria. The disclosures of this article and of the patents cited in this specification are incorporated herein by references.
It is known to incorporate cosmetic and therapeutic compositions, including emulsions thereof, into fibrous articles or sheets and to package the articles in vapor-and moisture-resistant containers such as polyethylene envelopes and the like, as described in U.S. Pat. Nos. 4,559,157, 2,999,265, 2,840,080, 3,624,224 and 3,896,807. Nevertheless, no high water content sunscreen agents, so far as is known, have been formulated specifically for application with a fibrous sheet material wherein the fibrous sheets are impregnated with the formulation and prepackaged in vapor-and moisture-impermeable containers.